Mirror assembly for light steering

ABSTRACT

Embodiments of the disclosure provide a Light Detection and Ranging (LiDAR) system that includes a light source configured to emit a light beam, a first apparatus configured to adjust the light beam and a second apparatus configured to adjust the light beam and receive the reflected light beam from the first apparatus and an object. The first apparatus includes a first rotatable mirror configured to receive and reflect the light beam, and a first actuator configured to rotate the first rotatable mirror. The second apparatus includes a second adjustable mirror configured to receive and propagate the light beam, and a second actuator configured to adjust the second adjustable mirror, and a detector configured to receive the light beam reflected by objects.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a continuation in part of U.S. patent applicationSer. No. 16/237,454, filed on Dec. 31, 2018, entitled “Mirror Assemblyfor Light Steering,” which is a continuation in part of U.S. patentapplication Ser. No. 16/213,992, filed on Dec. 7, 2018, entitled “MirrorAssembly for Light Steering,” both of which are hereby incorporated byreference in their entireties.

BACKGROUND

Light steering typically involves the projection of light in apre-determined direction to facilitate, for example, the detection andranging of an object, the illumination and scanning of an object, or thelike. Light steering can be used in many different fields ofapplications including, for example, autonomous vehicles, medicaldiagnostic devices, etc.

Light steering can be performed in both transmission and reception oflight. For example, a light steering system may include a micro-mirrorarray to control the projection direction of light to detect/image anobject. Moreover, a light steering receiver may also include amicro-mirror array to select a direction of incident light to bedetected by the receiver, to avoid detecting other unwanted signals. Themicro-mirror array may include an array of micro-mirror assemblies, witheach micro-mirror assembly comprising a micro-mirror and an actuator. Ina micro-mirror assembly, a mirror-mirror can be connected to a substratevia a connection structure (e.g., a torsion bar, a spring, etc.) to forma pivot, and the micro-mirror can be rotated around the pivot by theactuator. Each micro-mirror can be rotated by a rotation angle toreflect (and steer) light from a light source towards at a targetdirection. Each micro-mirror can be rotated by the actuator to provide afirst range of angles of projection along a vertical axis and to providea second range of angles of projection along a horizontal axis. Thefirst range and the second range of angles of projection can define atwo-dimensional field of view (FOV) in which light is to be projected todetect/scan an object. The FOV can also define the direction of incidentlights, reflected by the object, are to be detected by the receiver.

The mirror assembly can dominate various performance metrics of thelight steering system including, for example, precision, actuationpower, FOV, dispersion angle, reliability, etc. It is desirable toprovide a mirror assembly that can improve these performance metrics.

BRIEF SUMMARY

In one aspect, embodiments of the disclosure provide a Light Detectionand Ranging system. The system may include a light source configured toemit a light beam, a first apparatus configured to adjust the light beamand a second apparatus configured to adjust the light beam and receivethe light beam from a first rotatable mirror and reflected by an object.The first apparatus may include the first rotatable mirror configured toreceive and reflect the light beam and a first actuator configured torotate the first rotatable mirror. The second apparatus may include asecond rotatable mirror configured to receive and propagate the lightbeam, a receiving mirror configured to receive and reflect the lightbeam reflected by an object and a second actuator configured to adjustthe second adjustable mirror and the receiving mirror. The system mayfurther include a detector configured to receive the light beamreflected by the receiving mirror.

In another aspect, embodiments of the disclosure provide a LightDetection and Ranging system. The system may include a light sourceconfigured to emit a light beam and a light adjusting aperture. Thelight adjusting aperture may include a motor configured to rotate theaperture in the first direction, a microelectromechanical system (MEMS)rotatable in a first direction and a detector configured to receive alight beam reflected by an object. The microelectromechanical system(MEMS) may include a rotatable mirror rotatable in a second direction,orthogonal to the first direction, configured to receive and reflect alight beam projected by the light source, and an actuator configured torotate the rotatable mirror in the second direction. The light adjustingapparatus may further include a detector configured to receive a lightbeam reflected by an object.

In a further aspect, embodiments of the disclosure further provide amethod for adjusting a light beam in a light steering system. The methodmay include determining a first angle and a second angle of a lightpath, the light path being a projection path for an output light or aninput path of an input light, the first angle being with respect to afirst dimension, the second angle being with respect to a seconddimension orthogonal to the first dimension and controlling an array offirst actuators to rotate an array of first rotatable micro-mirrors of amicroelectromechanical system (MEMS) to set the first angle. The methodmay also include controlling a second non-MEMS system to set the secondangle and projecting, using a light source, a light beam including alight signal towards a mirror assembly, corresponding to the controlledarray of first actuators and the controlled non-MEMS system at the setfirst and second angle. The method may further include receiving areflection of the light beam, reflected by an object, by a detectorincluded by the non-MEMS system.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory onlyand are not restrictive of the invention, as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The detailed description is set forth with reference to the accompanyingfigures.

FIG. 1 shows an autonomous driving vehicle utilizing aspects of certainembodiments of the disclosed techniques herein.

FIGS. 2A-2B illustrate an example of a light steering system, accordingto certain embodiments.

FIG. 3A-FIG. 3E illustrate an example of a mirror assembly and itsoperations, according to certain embodiments.

FIG. 4 illustrates an example of operation of the mirror assembly ofFIG. 3A-FIG. 3E to provide a two-dimensional field of view (FOV),according to certain embodiments.

FIG. 5A and FIG. 5B illustrate another example of a mirror assembly,according to certain embodiments.

FIG. 6 illustrates another example of a mirror assembly, according tocertain embodiments.

FIG. 7 illustrates another example of a mirror assembly, according tocertain embodiments.

FIG. 8 illustrates another example of a mirror assembly, according tocertain embodiments.

FIG. 9 illustrates a flowchart of a method of operating a mirrorassembly, according to embodiments of the disclosure.

FIG. 10 illustrates an example computer system that may be utilized toimplement techniques disclosed herein.

FIG. 11 illustrates another example of a light steering system,according to certain embodiments.

FIG. 12 illustrates another example of a light steering system,according to certain embodiments.

FIG. 13 illustrates a flowchart of method of operating a mirrorassembly, according to embodiments of the disclosure.

DETAILED DESCRIPTION

Aspects of the present disclosure relate generally to peripheraldevices, and in particular to a wireless peripheral device controller,according to certain examples.

In the following description, various examples of a mirror assembly anda light steering system will be described. For purposes of explanation,specific configurations and details are set forth in order to provide athorough understanding of the embodiments. However, it will be apparentto one skilled in the art that certain embodiments may be practiced orimplemented without every detail disclosed. Furthermore, well-knownfeatures may be omitted or simplified in order to prevent anyobfuscation of the novel features described herein.

Light steering can be found in different applications. For example, aLight Detection and Ranging (LiDAR) module of a vehicle may include alight steering system. The light steering system can be part of thetransmitter to steer light towards different directions to detectobstacles around the vehicle and to determine the distances between theobstacles and the vehicle, which can be used for autonomous driving.Moreover, a light steering receiver may also include a micro-mirrorarray to select a direction of incident light to be detected by thereceiver, to avoid detecting other unwanted signals. Further, the headlight of a manually-driven vehicle can include the light steeringsystem, which can be controlled to focus light towards a particulardirection to improve visibility for the driver. In another example,optical diagnostic equipment, such as an endoscope, can include a lightsteering system to steer light in different directions onto an object ina sequential scanning process to obtain an image of the object fordiagnosis.

Light steering can be implemented by way of a micro-mirror array. Themicro-mirror array can have an array of micro-mirror assemblies, witheach micro-mirror assembly having a movable micro-mirror and an actuator(or multiple actuators). The micro-mirrors and actuators can be formedas microelectromechanical systems (MEMS) on a semiconductor substratewhich allows integration of the MEMS with other circuitries (e.g.,controller, interface circuits, etc.) on the semiconductor substrate. Ina micro-mirror assembly, a mirror-mirror can be connected to thesemiconductor substrate via a connection structure (e.g., a torsion bar,a spring, etc.) to form a pivot. The actuator can rotate themicro-mirror around the pivot, with the connection structure deformed toaccommodate the rotation. The array of micro-mirrors can receiveincident light beam, and each micro-mirror can be rotated at a commonrotation angle to project/steer the incident light beam at a targetdirection. Each micro-mirror can be rotated around two orthogonal axesto provide a first range of angles of projection along a verticaldimension and to provide a second range of angles of projection along ahorizontal dimension. The first range and the second range of angles ofprojection can define a two-dimensional field of view (FOV) in whichlight is to be projected to detect/scan an object. The FOV can alsodefine the direction of incident lights, reflected by the object, are tobe detected by the receiver.

In some examples, each micro-mirror assembly may include a singlemicro-mirror. The single micro-mirror can be coupled with a pair ofactuators on a frame of a gimbal structure and rotatable on a firstaxis. The frame of the gimbal structure is further coupled with thesemiconductor substrate and rotatable on a second axis orthogonal to thefirst axis. A first pair of actuators can rotate the mirror around thefirst axis with respect to the frame to steer the light along a firstdimension, whereas a second pair of actuators can rotate the framearound a second axis to steer the light along a second dimension.Different combinations of angle of rotations around the first axis andthe second axis can provide a two-dimensional FOV in which light is tobe projected to detect/scan an object. The FOV can also define thedirection of incident lights, reflected by the object, are to bedetected by the receiver.

Although such arrangements allow the projection of light to form atwo-dimensional FOV, there may be a number of potential disadvantages.First, having a single mirror to provide light steering can require arelatively high actuation force to achieve a target FOV and a targetdispersion, which can reduce reliability. More specifically, to reducedispersion, the size of the mirror can be made to match the width of thelight beam from the light source, which leads to increased mass andinertia of the mirror. As a result, a larger actuation force (e.g.,torque) may be needed to rotate the mirror to achieve a target FOV. Thetorque required typically is in the order of micro N-m. Subjecting theactuators to larger actuation forces, especially for MEMS actuators, canshorten the lifespan and reduce the reliability of the actuators.Moreover, the reliability of the MEMS actuators may be further degradedwhen the light steering system relies solely on the single mirror tosteer the light, which can become a single point of failure.

Conceptual Overview of Certain Embodiments

Examples of the present disclosure relate to a light steering systemthat can address the problems described above. Various embodiments ofthe light steering system can include a plurality of mirrors to performlight steering, such as those shown and described below with respect toFIG. 3A-FIG. 3E, FIG. 5A, FIG. 6, FIG. 7 and FIG. 8. The light steeringsystem can be used as part of a transmitter to control a direction ofprojection of output light. The light steering system can also be usedas part of a receiver to select a direction of input light to bedetected by the receiver. The light steering system can also be used ina coaxial configuration such that the light steering system can projectoutput light to a location and detects light reflected from thatlocation.

In some embodiments, a light steering system may include a light source,a first rotatable mirror, a second rotatable mirror, and a receiver. Thefirst rotatable mirror and the second rotatable mirror can define anoutput projection path for light transmitted by the light source, or toselect an input path for input light to be received by the receiver. Thefirst rotatable mirror and the second rotatable mirror can be rotatableto steer the output projection path at different angles with respect to,respectively, a first dimension and a second dimension orthogonal to thefirst dimension, to form a two-dimensional FOV.

The light steering system may further include a first actuatorconfigured to rotate the first rotatable mirror around a first axis, asecond actuator configured to rotate the second rotatable mirror arounda second axis orthogonal to the first axis, and a controller coupledwith the first actuator and the second actuator. The controller maycontrol the first actuator and the second actuator to apply a firsttorque and a second torque to rotate, respectively, the first rotatablemirror and the second rotatable mirror along, respectively, the firstaxis and the second axis. The controller can control the first actuatorand the second actuator to steer the output projection path at differentangles with respect to the first dimension and the second dimensionaccording to a movement sequence, such as those shown and describedbelow with respect to FIG. 4 and FIG. 5B, to create the two-dimensionalFOV.

In some embodiments, the first rotatable mirror and the second rotatablemirror can be arranged on the same surface of a semiconductor substrate,as shown in FIG. 3A. The light steering system can further include astationary third mirror stacked on top of the semiconductor substrateand facing the surface of the semiconductor substrate. As shown in FIG.3B, light from the light source, or input light from the environment,can be reflected by the first rotatable mirror, which can set a firstangle of the output projection path of the light with respect to thefirst dimension (e.g., an x-axis or a y-axis). The light reflected bythe first rotatable mirror can reach the third mirror, which may reflectthe light towards the second rotatable mirror. The second rotatablemirror can set an angle of the output projection path or an input pathwith respect to the second dimension (e.g., the z-axis of FIG. 4D).Different values of the first angle and the second angle can be obtainedby rotating the first rotatable mirror and the second rotatable mirrorto form the FOV.

In some embodiments, as shown in FIG. 3A, the light steering system caninclude a first array of mirrors including the first rotatable mirror,with each rotatable mirror of the array rotatable around the first axis,and a single second rotatable mirror rotatable around the second axis.In some embodiments, as shown in FIG. 5A, the light steering system canalso include a single first rotatable mirror, and an array of secondrotatable mirrors, with each rotatable mirror of the array rotatablearound the second axis. In some embodiments, as shown in FIG. 6, thelight steering system can also include a first array of rotatablemirrors and a second array of rotatable mirrors. The first array ofrotatable mirrors may be rotatable around the first axis. Moreover, thesecond array of mirrors may be rotatable around the second axis.

In some embodiments, the first rotatable mirror and the second rotatablemirror can be arranged on two different semiconductor substrates, asshown and described below with respect to FIG. 7. The first rotatablemirror can be arranged on a first surface of the first semiconductor,whereas the second rotatable mirror can be arranged on a second surfaceof the second semiconductor, with the first surface facing the secondsurface. Light from the light source can be reflected by the firstrotatable mirror, which can set the first angle of the output projectionpath or input path with respect to the first dimension (e.g., the x-axisor the y-axis). The light reflected by the first rotatable mirror canreach the second rotatable mirror, which can rotate around the secondaxis to set a second angle of the output projection path or the inputpath with respect to the second dimension (e.g., the z-axis).

Compared with an arrangement where a light steering system uses a singlemirror having two axis of rotation to provide two ranges of projectionor input angles to form a FOV, certain embodiments of the presentdisclosure can use a first rotatable mirror and a second rotatablemirror (or an array of first rotatable mirrors and a second rotatablemirror) with each having a single but orthogonal rotational axis toprovide the two ranges of angles that form the FOV. Such arrangementscan improve reliability (especially where the mirrors are MEMS devices)and precision, and can reduce actuation power, while providing the sameor superior FOV and dispersion. First, by using two mirrors to providetwo ranges of angles to provide the same FOV as the single mirror, someof the mirrors can be made smaller than the single mirror and mayrequire less actuation force to rotate than the single mirror. Theactuation of the two different mirrors can also be independentlyoptimized to further reduce the total actuation force. The reduction ofthe actuation forces can also reduce the burden on the actuators andincreases the lifespan of the actuators. Moreover, due to the smallermirrors, embodiments of the present disclosure can provide a larger FOVcompared with the single mirror implementation in response to the sameactuation force. The mirrors can be configured to provide the samemirror surface area as the single mirror, which can provide the samedispersion as the single mirror. In addition, where a plurality ofmirrors is involved in the steering of light, the likelihood that any ofthe mirrors becoming a single source of failure can be mitigated, whichcan further improve reliability. All of these can improve the robustnessand performance of a light steering system over conventionalimplementations.

Typical System Environment for Certain Embodiments

FIG. 1 illustrates an autonomous vehicle 100 in which the disclosedtechniques can be implemented. Autonomous vehicle 100 includes a LiDARsystem 102. LiDAR system 102 allows autonomous vehicle 100 to performobject detection and ranging in a surrounding environment. Based on theresult of object detection and ranging, autonomous vehicle 100 canmaneuver to avoid a collision with the object. LiDAR system 102 caninclude a light steering system 104 and a receiver 106. Light steeringsystem 104 can project one or more light signals 108 at variousdirections at different times in any suitable scanning pattern, whilereceiver 106 can monitor for a light signal 110 which is generated bythe reflection of light signal 108 by an object. Light signals 108 and110 may include, for example, a light pulse, a frequency modulatedcontinuous wave (FMCW) signal, an amplitude modulated continuous wave(AMCW) signal, etc. LiDAR system 102 can detect the object based on thereception of light signal 110, and can perform a ranging determination(e.g., a distance of the object) based on a time difference betweenlight signals 108 and 110. For example, as shown in FIG. 1, LiDAR system102 can transmit light signal 108 at a direction directly in front ofautonomous vehicle 100 at time T1 and receive light signal 110 reflectedby an object 112 (e.g., another vehicle) at time T2. Based on thereception of light signal 110, LiDAR system 102 can determine thatobject 112 is directly in front of autonomous vehicle 100. Moreover,based on the time difference between T1 and T2, LiDAR system 102 canalso determine a distance 114 between autonomous vehicle 100 and object112. Autonomous vehicle 100 can adjust its speed (e.g., slowing orstopping) to avoid collision with object 112 based on the detection andranging of object 112 by LiDAR system 102.

FIG. 2A-2B illustrate examples of internal components of a LiDAR system102. LiDAR system 102 includes a transmitter 202, a receiver 204, aLiDAR controller 206 which controls the operations of transmitter 202and receiver 204. Transmitter 202 includes a light source 208 and acollimator lens 210, whereas receiver 204 includes a collimator lens 214and a photodetector 216. LiDAR system 102 further includes a mirrorassembly 212 and a beam splitter 213. In LiDAR system 102, transmitter202 and receiver 204 can be configured as a coaxial system to sharemirror assembly 212 to perform light steering operation, with beamsplitter 213 configured to reflect incident light reflected by mirrorassembly 212 to receiver 204.

FIG. 2 A illustrates a light projection operation. To project light,LiDAR controller 206 can control light source 208 (e.g., a pulsed laserdiode, a source of FMCW signal, AMCW signal, etc.) to transmit lightsignal 108 as part of collimated light beam 218. Collimated light beam218 can disperse upon leaving light source 208 and can be converted intocollimated light beam 218 by collimator lens 210.

Collimated light beam 218 can be incident upon mirror assembly 212,which can reflect and steer the light beam along an output projectionpath 219 towards object 112. Mirror assembly 212 can include one or morerotatable mirrors. FIG. 2 A illustrates mirror assembly 212 as havingone mirror, but as to be described below, in some embodiments, mirrorassembly 212 may include a plurality of mirrors.

Collimated light beam 218 may disperse upon leaving the surface ofmirror surface of mirror assembly 212. Collimated light beam 218 canform a dispersion angle with respect to projection path 219 over thelength and the width of the mirror surface. The dispersion angle ofcollimated light beam 218 can be given by the following equation:

$\begin{matrix}{\alpha = \frac{\lambda}{D \times \pi}} & \left( {{Equation}\mspace{14mu} 1} \right)\end{matrix}$

In Equation 1, a is the dispersion angle, is the wavelength of lightbeam 218, whereas D is the length (or width) of the mirror surface.Light beam 218 can disperse at a dispersion angle α_(L) with respect tooutput projection path 219 over the length (L) of the mirror surface,and at a dispersion angle α_(W) with respect to projection path 219 overthe width (W) of the mirror surface. It is desirable to reduce thedispersion angle to focus the light beam power along projection path219, to improve the resolution of object detection, ranging, andimaging. To reduce the dispersion angle, the length and width D of themirror surface can be increased to match with the aperture length.

Mirror assembly 212 further includes one or more actuators (not shown inFIG. 2A) to rotate the rotatable mirrors. The actuators can rotate therotatable mirrors around a first axis 222 and can rotate the rotatablemirrors along a second axis 226. As described in more detail below, therotation around first axis 222 can change a first angle 224 of outputprojection path 219 with respect to a first dimension (e.g., thex-axis), whereas the rotation around second axis 226 can change a secondangle 228 of output projection path 219 with respect to a seconddimension (e.g., the z-axis). LiDAR controller 206 can control theactuators to produce different combinations of angles of rotation aroundfirst axis 222 and second axis 226 such that the movement of outputprojection path 219 can follow a scanning pattern 232. A range 234 ofmovement of output projection path 219 along the x-axis, as well as arange 238 of movement of output projection path 219 along the z-axis,can define a FOV. An object within the FOV, such as object 112, canreceive and reflect collimated light beam 218 to form reflected lightsignal, which can be received by receiver 204.

FIG. 2B illustrates a light detection operation. LiDAR controller 206can select an incident light direction 239 for detection of incidentlight by receiver 204. The selection can be based on setting the anglesof rotation of the rotatable mirrors of mirror assembly 212, such thatonly divert light beam 220 propagating along incident light direction239 gets reflected to beam splitter 213, which can then divert lightbeam 220 to photodetector 216 via collimator lens 214. With sucharrangements, receiver 204 can selectively receive signals that arerelevant for the ranging/imaging of object 112, such as light signal 110generated by the reflection of collimated light beam 218 by object 112,and not to receive other signals. As a result, the effect of environmentdisturbance on the ranging/imaging of the object can be reduced, and thesystem performance can be improved.

Examples of Mirror Assemblies

FIG. 3A-FIG. 3E illustrate an example of a mirror assembly 300,according to embodiments of the present disclosure. Mirror assembly 300can be part of the light steering system. FIG. 3A illustrates a top viewof mirror assembly 300, FIG. 3B illustrates a perspective view of mirrorassembly 300, whereas FIG. 3C illustrates a side view of mirror assembly300. As shown in FIG. 3A, mirror assembly 300 can include an array offirst rotatable mirrors 302, a second rotatable mirror 304, and astationary mirror 306. The total mirror surface area of the array offirst rotatable mirrors 302 is identical to the mirror surface area ofsecond rotatable mirror 304 and of stationary mirror 306. The array offirst rotatable mirrors 302 and second rotatable mirror 304 can be MEMSdevices implemented on a surface 308 of a semiconductor substrate 310.Stationary mirror 306 can be positioned above semiconductor substrate310. In some embodiments, stationary mirror 306 can be included withinthe same integrated circuit package as semiconductor substrate 310 toform an integrated circuit. In some embodiments, stationary mirror 306can also be positioned external to the integrated circuit package thathouses semiconductor substrate 310.

Referring to FIG. 3B and FIG. 3C, in one configuration, array of firstrotatable mirrors 302 can receive collimated light beam 218 fromcollimator lens 210, reflect collimated light beam 218 towardsstationary mirror 306, which can reflect collimated light beam 218towards second rotatable mirror 304. Second rotatable mirror 304 canreflect collimated light beam 218 received from stationary mirror 306 asan output along output projection path 219. In another configuration(not shown in the figures), second rotatable mirror 304 can receivecollimated light beam 218 from collimator lens 210 and reflectcollimated light beam 218 towards stationary mirror 306, which canreflect collimated light beam 218 towards array of first rotatablemirrors 302. Array of first rotatable mirrors 302 can reflect collimatedlight beam 218 as an output along output projection path 219. In a casewhere mirror assembly 300 is part of the receiver, the array of firstrotatable mirrors 302 and second rotatable mirror 304 can also selectincident light direction 239 for receiver 204 similar to the selectionof direction of output projection path 219. As described in furtherdetail below, array of first rotatable mirrors 302 and second rotatablemirror 304 change an angle of output projection path 219 with respectto, respectively, the x-axis and the z-axis, to form a two-dimensionalFOV.

As described above, the total mirror surface area of the array of firstrotatable mirrors 302 is identical to the mirror surface area of secondrotatable mirror 304 and of stationary mirror 306. Moreover, eachdimension (e.g., length and width) of the mirror surface area providedby each of the array of first rotatable mirrors 302, second rotatablemirror 304, and stationary mirror 306 can match the aperture length ofcollimator lens 210. With such arrangements, each of the array of firstrotatable mirrors 302, second rotatable mirror 304, and stationarymirror 306 can receive and reflect a majority portion of collimatedlight beam 218.

Moreover, as shown in FIG. 3C, the separation between stationary mirror306 and surface 308 (which includes an array of first rotatable mirrors302 and second rotatable mirror 304, denoted as d1, as well as theseparation between the center points of an array of first rotatablemirrors 302 and second rotatable mirror 304, denoted as d2, can berelated to incident angle θ of collimated light beam 218 with respect tothe z-axis, as follows:

$\begin{matrix}{\frac{\frac{d\; 2}{2}}{d\; 1} = {\tan (\theta)}} & \left( {{Equation}\mspace{14mu} 2} \right)\end{matrix}$

In Equation 2, the ratio between half of d2 (the distance between thecenter points of an array of first rotatable mirrors 302 and secondrotatable mirror 304) and d1 (the distance between stationary mirror 306and surface 308) can be defined by applying tangent function to theincident angle θ of collimated light beam 218.

Referring back to FIG. 3A, each rotatable mirror of the array of firstrotatable mirrors 302 (e.g., first rotatable mirror 302 a) is rotatablearound a first axis 314, whereas second rotatable mirror 304 isrotatable around a second axis 316 which is orthogonal to first axis314. Each rotatable mirror of the array of first rotatable mirrors 302,as well as second rotatable mirror 304, is coupled with a pair of rotaryactuators, such as comb drive, piezoelectric device, electromagneticdevice, etc., to rotate the mirror. For example, first rotatable mirror302 a is coupled with and rotary actuators 322 a and 322 b, whereassecond rotatable mirror 304 is coupled with rotary actuators 324 a and324 b. Each of first rotatable mirror 302 a (and the rest of array offirst rotatable mirrors 302) and second rotatable mirror 304 canindependently move output projection path 219 along, respectively, thex-axis and the z-axis, to form a FOV.

FIG. 3D illustrates an example of setting an angle of output projectionpath 219 with respect to the x-axis based on the rotation movement offirst rotatable mirror 302 a. FIG. 3D shows a side view of firstrotatable mirror 302 a with first axis 314, stationary mirror 306, andsecond rotatable mirror 304. First axis 314 is aligned with the y-axis.The dotted lines show the orientations of first rotatable mirror 302 aand normal vector 330 of first rotatable mirror 302 a before rotation,while the solid lines show the orientations of first rotatable mirror302 a and normal vector 330 after a counter-clockwise rotation. As firstrotatable mirror 302 a rotates counter-clockwise, normal vector 330 offirst rotatable mirror 302 a also rotates counter-clockwise, and theangle of incidence 332 of collimated light beam 218 with respect to therotated normal vector 330 reduces. As the angle of reflection 334 ofcollimated light beam 218 is equal to the angle of incidence 332, thereflected collimated light beam 218 also rotates counter-clockwise andhit stationary mirror 306 at an increased angle 336. Collimated lightbeam 218 is also reflected from stationary mirror 306 at the same angle336 towards second rotatable mirror 304, which can reflect light beam218 along output projection path 219 or incident light direction 239that also forms angle 336 with the x-axis. Each rotatable mirror of thearray of first rotatable mirrors 302 can be controlled to rotate by thesame angle of rotation and at the same direction (clockwise orcounterclockwise) around first axis 314, so that the array cancollectively set output projection path 219 of collimated light beam218, or incident light direction 239, to form angle 336 with respect tothe x-axis.

FIG. 3E illustrates an example of movement of output projection path 219based on the rotation movement of second rotatable mirror 304. FIG. 3Eis a side view of second rotatable mirror 304 with second axis 316pointing out of paper. The dotted lines show the orientations of secondrotatable mirror 304 and normal vector 340 of second rotatable mirror304 before rotation, while the solid lines show the orientations ofsecond rotatable mirror 304 and normal vector 340 after acounter-clockwise rotation. As second rotatable mirror 304 rotatescounter-clockwise, normal vector 340 of second rotatable mirror 304 alsorotates counter-clockwise, and the angle of incidence 342 of collimatedlight beam 218 with respect to the rotated normal vector 340 reduces. Asthe angle of reflection 344 of collimated light beam 218 is equal to theangle of incidence 342, output projection path 219 of reflectedcollimated light beam 218 moves along the z-axis by a distance d4 asindicated by the arrow. Combined with the rotation of first rotatablemirror 302 a, output projection path 219 can move along both the x-axisand the z-axis to form a two-dimensional FOV. It is understood thatincident light direction 239 can also be adjusted based on the rotationmovement of second rotatable mirror 304 in a similar fashion as outputprojection path 219.

FIG. 4 illustrates an example operation of mirror assembly 300 toprovide a two-dimensional FOV. The diagram on the top of FIG. 4illustrates a movement sequence 400 of an angle of output projectionpath 219 provided by the rotations of array of first rotatable mirrors302 and second rotatable mirror 304. As shown in FIG. 4, LiDARcontroller 206 can control rotary actuators 324 a and 324 b to rotatesecond rotatable mirror 304 to set different angles of output projectionpath 219 with respect to the z-axis, for example, at angles representedby points 402 and 404, to within a first angle range 406. LiDARcontroller 206 can also control the rotary actuators of array of firstrotatable mirrors 302 (e.g., rotary actuators 322 a and 322 b) to setdifferent angles of output projection path 219 with respect to thex-axis, for example, at angles represented by points 412 and 414, toprovide a second angle range 416, and the two angle ranges can define aFOV.

The figure on the bottom of FIG. 4 illustrates a control signalssequence 430, with respect to time, to generate movement sequence 400 ofoutput projection path 219. In some embodiments, movement sequence 400can be provided to LiDAR controller 206, which can generate controlsignals sequence 430 based on movement sequence 400. Control signalssequence 430 comprises first dimension control signals sequences 432,434, 436, etc., of control signals for the rotary actuators of secondrotatable mirrors 304 to change the angle of output projection path 219(or incident light direction 239) with respect to a first dimension(e.g., z-axis). Control signals sequence 430 further include a seconddimension control signal between two first dimension control signalssequences. For example, there is a second dimension control signal 440between first dimension control signals sequences 432 and 434. Further,there is a second dimension control signal 442 between first dimensioncontrol signals sequences 434 and 436. The second dimension controlsignals are for the rotary actuators of array of first rotatable mirrors302 to change the angle of output projection path 219 (or incident lightdirection 239) with respect to a second dimension (e.g., x-axis).

Each control signal in control signals sequences 432, 434, 436, etc.,can cause the rotary actuators of second rotatable mirror 304 togenerate a torque force to increment the angle of rotation of the secondrotatable mirror 304 around second axis 316. For example, firstdimension control signal 432 a can correspond to point 402, whereasfirst dimension control signal 432 b can correspond to point 404. Eachof first dimension control signals sequences 432, 434, and 436 can causea sweep of angles of output projection path 219 (or incident lightdirection 239) across first angle range 406 with respect to the z-axisby controlling the angle of rotation of the second rotatable mirror. Atthe end of first angle range 406, a second dimension control signal canbe provided to change the angle of projection path 219 (or incidentlight direction 239) with respect to the x-axis before the next firstdimension control signals sequence starts. For example, first dimensioncontrol signal 432 n corresponds to point 412 which is at the end offirst angle range 406. Following first dimension control signal 432 b issecond dimension control signal 440, which can rotate array of firstrotatable mirrors 302 to move output projection path 219 (or incidentlight direction 239) from points 412 to 414 along the x-axis. Followingsecond dimension control signal 440, first dimension control signalssequence 434 starts, and first dimension control signal 434 a can rotatesecond rotatable mirror 304 to move the angle of output projection path219 (or incident light direction 239) with respect to the z-axis from anangle represented by point 414 to an angle represented by 418, whilekeeping the angle with respect to the x-axis constant.

In some embodiments, first dimension control signals and seconddimension control signals can be independently optimized to reduce totalactuation forces and power. For example, first dimension control signalscan be provided to the rotary actuators at a relatively high frequencyclose to the natural frequency of second rotatable mirror 304 to induceharmonic resonance of the mirror. Such arrangements allow use of smallertorques to rotate second rotatable mirror 304, which is advantageousgiven that second rotatable mirror 304 can be the largest mirror withinmirror assembly 300 and has considerable mass and inertia. On the otherhand, second dimension control signals can be provided to the rotaryactuators at a relatively low frequency to operate each rotatable mirrorof array of first rotatable mirrors 302 as quasi-static loads. Thetorques required to rotate the mirrors of array of first rotatablemirrors 302 may be relatively low, given that the mirrors are small andhave small mass and inertia. In some embodiments, first dimensioncontrol signals can be in the form of high frequency sinusoidal signals,pulse width modulation (PWM) signals, etc., whereas second dimensioncontrol signals can be in the form of low frequency saw-tooth signals.

In some embodiments, in addition to movement sequence 400, a feedbackmechanism can also be provided to LiDAR controller 206 to generatecontrol signals sequence 430. The feedback mechanism includes a set ofsensors (e.g., capacitive sensors) to measure actual angles of rotationat the rotary actuators. The feedback mechanism enables LiDAR controller206 to adjust the first dimension and second dimension control signalsprovided to the rotary actuators based on monitoring the actual angle ofrotations at the rotary actuators, to improve the precision of the lightsteering operation. The adjustment can be performed to compensate for,for example, uncertainties and mismatches in the masses of the mirrors,driving strength of the rotary actuators, etc.

As an example, LiDAR controller 206 can perform adjustment of the firstdimension and second dimension control signals in a calibrationsequence. LiDAR controller 206 may store a set of initial settings(e.g., voltage, current, etc.) for the first dimension and seconddimension control signals based on a set of expected masses of themirrors and driving strength of the rotary actuators. During thecalibration process, LiDAR controller 206 can provide different firstdimension and second dimension control signals to create differentangles of rotations at the rotary actuators. LiDAR controller 206 canmonitor the actual angles of rotations at the rotary actuators when thefirst dimension and second dimension control signals are provided,compare the actual angles of rotations against the target angles ofrotations to determine differences, and adjust the first dimension andsecond dimension control signals to account for the differences. Forexample, each rotatable mirror of array of first rotatable mirrors 302is supposed to rotate at the same angle of rotation. LiDAR controller206 can measure the actual angles of rotation of each rotatable mirrorof array of first rotatable mirrors 302 using the capacitive sensors anddetermine a deviation of each actual angle from the target angle ofrotation for each rotatable mirror. LiDAR controller 206 can adjust thesecond dimension control signals for the rotary actuators of eachrotatable mirror (e.g., rotary actuators 322 a and 322 b) based on thedeviations to ensure that each rotatable mirror rotates by the sametarget angle of rotation.

Compared with a single mirror assembly, mirror assembly 300 can providesame or superior FOV and dispersion performance while reducing theactuation force and power and improving reliability. First, eachrotatable mirror of the array of first rotatable mirrors 302 issubstantially smaller than a single mirror having a comparable lengthand width and dispersion performance, even if the mirrors are driven asquasi-static loads. As a result, each rotatable mirror of the array offirst rotatable mirrors 302 requires substantially smaller torque toprovide the same FOV as the single mirror assembly. Moreover, althoughthe mirror surface area of the second rotatable mirror 304 is similar tothe area of the single mirror arrangement, the torque needed to rotatesecond rotatable mirror 304 can be substantially reduced by drivingsecond rotatable mirror 304 at close to a natural frequency to induceharmonic resonance. Such arrangements allow substantial reduction in therequired torque to achieve a target FOV. The reduction of torque alsoreduces the burden on the rotary actuators and increases their lifespan.In addition, as a plurality of mirrors are involved in the steering oflight, the likelihood of any of the mirror becoming a single source offailure can be mitigated, which can further improve reliability.

FIG. 5A illustrates another example of a mirror assembly 500, accordingto embodiments of the present disclosure. Mirror assembly 500 can bepart of a light steering system. As shown in FIG. 5A, mirror assembly500 can include a first rotatable mirror 502, an array of secondrotatable mirrors 504, and stationary mirror 306. Each of firstrotatable mirror 502, array of second rotatable mirror 504, andstationary mirror 306 can have substantially same mirror surface areaand can have dimensions matching the aperture length of lens 210, as inother examples described above. First rotatable mirror 502, an array ofsecond rotatable mirrors 504 can be MEMS devices implemented on asurface 508 of a semiconductor substrate 510.

Stationary mirror 306 can be positioned above semiconductor substrate510. First rotatable mirror 502 may receive collimated light beam 218from lens 210, reflect the collimated light beam 218 towards stationarymirror 306, which can in turn reflect collimated light beam 218 towardsarray of second rotatable mirrors 504. Array of second rotatable mirrors504 can reflect the collimated light beam 218 received from stationarymirror 306 as output along output projection path 219. First rotatablemirror 502 is rotatable around a first axis 514, whereas each rotatablemirror of the array of second rotatable mirrors 504 is rotatable arounda second axis 516 which is orthogonal to first axis 514. Just as arrayof first rotatable mirrors 302 of FIG. 3A, the rotation of firstrotatable mirror 502 can set an angle of output projection path 219 (orincident light direction 239) with respect to the x-axis, whereas therotation of array of second rotatable mirrors 504 can set an angle ofoutput projection path 219 (or incident light direction 239) withrespect to the z-axis.

First rotatable mirror 502 and array of second rotatable mirror 504 canindependently change the angle of output projection path 219 (orincident light direction 239) with respect to, respectively, the x-axisand the z-axis, to form a two-dimensional FOV. The rotation of firstrotatable mirror 502 and array of second rotatable mirrors 504 can becontrolled based on a movement sequence 550 of FIG. 5B. First rotatablemirror 502 can be controlled by first dimension control signals to moveoutput projection path 219 (or incident light direction 239) along thex-axis within a movement range 552, whereas array of second rotatablemirrors 504 can be controlled by second dimension control signals tomove projection path along the z-axis within a movement range 554.Similar to the arrangements described in FIG. 4, first dimension controlsignals can be provided at a relatively high frequency close to thenatural frequency of first rotatable mirror 502 to induce harmonicresonance, whereas second dimension control signals can be provided at arelatively low frequency to drive each of the array of second rotatablemirrors 504 as quasi-static loads.

In some examples, a mirror assembly can include two arrays of rotatablemirrors to perform light steering along a first dimension (e.g., thex-axis) and a second dimension (e.g., the z-axis). FIG. 6 illustrates anexample of a mirror assembly 600 that includes array of first rotatablemirrors 302 of FIG. 3A and array of second rotatable mirrors 504 of FIG.5A on a surface 608 of a semiconductor substrate 610. Mirror assembly600 further includes stationary mirror 306 positioned abovesemiconductor substrate 610. Array of first rotatable mirrors 302 isrotatable around first axis 314, whereas array of second rotatablemirrors 504 is rotatable around second axis 516 which is orthogonal tofirst axis 314. Array of first rotatable mirrors 302 and array of secondrotatable mirror 504 can independently change the angle of outputprojection path 219 with respect to, respectively, the x-axis and thez-axis, to form a two-dimensional FOV as described above.

FIG. 7 illustrates another example of a mirror assembly 700, accordingto embodiments of the present disclosure. Mirror assembly 700 can bepart of the light steering system. The top figure of FIG. 7 shows a topview of mirror assembly 700, whereas the bottom figure of FIG. 7 shows aperspective view of mirror assembly 700. As shown in FIG. 7, mirrorassembly 700 can include array of first rotatable mirrors 302, a secondrotatable mirror 704, and an optional mirror 706 which can be stationaryor rotatable. Array of first rotatable mirrors 302 and mirror 706 can beimplemented as a surface 708 of a first semiconductor substrate 710,whereas second rotatable mirror 704 can be implemented on a secondsemiconductor substrate (not shown in FIG. 7) and facing array of firstrotatable mirrors 302 and mirror 706. Each of array of first rotatablemirrors 302, second rotatable mirror 704, and mirror 706 may havesubstantially identical mirror surface area having each dimensionmatching the aperture length of collimator lens 210, as in otherexamples described above. Array of first rotatable mirrors 302 canreceive collimated light beam 218 (or divert light beam 220) and reflectthe light towards second rotatable mirror 704, which can reflect thelight from array of first rotatable mirrors 302 towards mirror 706.Mirror 706 can reflect the light received from second rotatable mirror704 as output along output projection path 219. Mirror 706 can alsoreflect input light towards second rotatable mirror 704, and only lightthat propagates along incident light direction 239 will be reflected toarray of first rotatable mirrors 302. Array of first rotatable mirrors302 is rotatable around first axis 314, whereas second rotatable mirror704 is rotatable around second axis 724 which is orthogonal to firstaxis 314. The rotation of each rotatable mirror of array of firstrotatable mirrors 302 can set an angle of output projection path 219 (orincident light direction 239) with respect to the x-axis, whereas therotation of second rotatable mirror 704 can set an angle of outputprojection path 219 (or incident light direction 239) with respect tothe z-axis. Mirror 706 can be stationary or can be rotatable to allowfurther adjustment of the direction of output projection path 219 (orincident light direction 239).

In some embodiments, mirror assembly 212 can have a fast axis (e.g., thex-axis) driven with a sinusoidal scanning trajectory and shifting thesample in steps or continuously in a slow axis (e.g., the z-axis) with asawtooth scanning trajectory or a triangle scanning trajectory. In someembodiments, the fast axis movement can be steered by MEMS devisessimilar to embodiments disclosed in FIG. 3A, FIG. 5A, FIG. 6 and FIG. 7,and the other axis (the slow axis) movements can be steered by non-MEMSdevices such as an analog system (e.g., a system that includes at leastone of a galvanometer mirror, a mirror polygon, or flash lens). As theslow axis scanning has a lower requirement for scanning frequency,accuracy and mechanical life, using suitable non-MEMS devices to drivethe slow axis scanning can meet the requirement while significantlyreducing the complexity and the cost of establishing the mirrorassembly. FIG. 8 illustrates another example of a mirror assembly 800,according to embodiments of the present disclosure. Mirror assembly 800can be part of the light steering system. As shown in FIG. 8, mirrorassembly 800 can include an array of first rotatable mirrors 802, asecond rotatable mirror 804 and stationary mirror 306. Each of array offirst rotatable mirrors 802, second rotatable mirror 804 and stationarymirror 306 can have substantially same mirror surface area and can havedimensions matching the aperture length of lens 210, as in otherexamples described above. Array of first rotatable mirrors 802 can beMEMS devices implemented on a surface 808 of a semiconductor substrate810. Second rotatable mirror 804 can be a non-MEMS device such as ananalog system (e.g., a galvanometer mirror, a mirror polygon, or flashlens devices) implemented on surface 808 of semiconductor substrate 810.Stationary mirror 306 can be positioned above semiconductor substrate810. Array of first rotatable mirrors 802 may receive collimated lightbeam 218 from lens 210, reflect the collimated light beam 218 towardsstationary mirror 306, which can in turn reflect collimated light beam218 towards second rotatable mirror 804. Second rotatable mirror 804 canreflect the collimated light beam 218 received from stationary mirror306 as output along output projection path 219. Each rotatable mirror ofarray of first rotatable mirrors 802 is rotatable around a first axis814, whereas second rotatable mirror 804 is rotatable around a secondaxis 816 which is different from first axis 814, such as orthogonal tofirst axis 814. Just as array of first rotatable mirrors 302 of FIG. 3A,the rotation of array of first rotatable mirrors 802 can set an angle ofoutput projection path 219 (or incident light direction 239) withrespect to the x-axis, whereas the rotation of second rotatable mirror804 can set an angle of output projection path 219 (or incident lightdirection 239) with respect to the z-axis.

Array of first rotatable mirrors 802 and second rotatable mirror 804 canindependently change the angle of output projection path 219 (orincident light direction 239) with respect to, respectively, the x-axisand the z-axis, to form a two-dimensional FOV. The rotation of array offirst rotatable mirrors 802 and second rotatable mirror 804 can becontrolled based on a movement sequence. Similar to the arrangementsdescribed in FIG. 4, first dimension control signals can be provided ata relatively high frequency close to the natural frequency of array offirst rotatable mirrors 802 to induce harmonic resonance, whereas seconddimension control signals can be provided at a relatively low frequencyto drive second rotatable mirror 804 as quasi-static loads.

FIG. 9 illustrates a flowchart of method of operating a mirror assembly,according to embodiments of the disclosure. FIG. 9 shows a simplifiedflow diagram of method 900 for performing light steering operation usinga mirror assembly, such as mirror assemblies 300, 500, 600,700 and 800of FIGS. 3A-FIG. 8. The mirror assembly comprises an array of firstrotatable mirrors (e.g., array of first rotatable mirrors 302, array ofsecond rotatable mirrors 504, etc.) and a second rotatable mirror (e.g.,second rotatable mirror 304, first rotatable mirror 502, secondrotatable mirror 704, etc.). The array of first rotatable mirrors may bepart of a MEMS system and the second adjustable mirror may be part of aMEMS system (e.g., in mirror assemblies 300, 500, 600 and 700) or anon-MEMS system (e.g., in mirror assemblies 800) such as an analogsystem that includes at least one of a galvanometer mirror, a mirrorpolygon or a flash lens. Method 900 may be performed by a controller,such as LiDAR controller 206.

At operation 902, the controller determines a first angle and a secondangle of a light path. In some embodiments, the light path may be one ofa projection path for output light or an input path of input light, thefirst angle may be with respect to a first dimension and the secondangle may be with respect to a second dimension orthogonal to the firstdimension. The first angle may be set according to a scanning pattern(e.g., a sinusoidal scanning trajectory along the fast axis) withinrange 234. The second angle may be set according to the scanning pattern(e.g., sawtooth scanning trajectory or a triangle scanning trajectoryalong the slow axis) within range 238.

At operation 904, the controller controls an array of first actuators torotate an array of first rotatable mirrors of the MEMS to set the firstangle. The controller may also control the array of first actuators toexert a torque to each rotatable mirror of the array of first rotatablemirrors as a quasi-static load.

At operation 906, the controller controls a second actuator of a MEMS ora non-MEMS system to set the second angle. In some embodiments, thecontroller may control the second actuator to exert a torque to thesecond rotatable mirror using a non-MEMS system (e.g., a galvanometermirror or a polygon mirror). In some other embodiments, the controllermay change the mirror within a flash system (e.g., an array of identicalmirrors) to move the light beam within range 238 of scanning pattern232. In some embodiments, the controller may control the second actuatorto exert a torque to the second rotatable mirror using a MEMS, similarto rotating the array of first rotatable mirrors of the MEMS to set thefirst angle.

At operation 908, the controller uses the array of first rotatablemirrors set at the first angle and the second rotatable mirror set atthe second angle to perform at least one of: reflecting the output lightfrom the light source along the projection path towards an object orreflecting the input light propagating along the input path to areceiver. For example, the controller may control a light source toproject a light beam including a light signal towards the mirrorassembly. The light source may include a pulsed laser diode, a source ofFMCW signal, a source of AMCW signal, etc. The controller may also usethe array of first rotatable mirrors and the second rotatable mirror todirect light signal reflected by the distant object to a receiver andnot to direct light signals received at other directions to thereceiver.

In some embodiments, the mentioned method 900 may be implemented on acomputer system utilizing any suitable number of subsystems. Examples ofsuch subsystems are shown in FIG. 10 in computer system 10. In someembodiments, a computer system includes a single computer apparatus,where the subsystems may be the components of the computer apparatus. Inother embodiments, a computer system may include multiple computerapparatuses, each being a subsystem, with internal components. Acomputer system may include desktop and laptop computers, tablets,mobile phones and other mobile devices. In some embodiments, a cloudinfrastructure (e.g., Amazon Web Services), a graphical processing unit(GPU), etc., may be used to implement the disclosed techniques,including the techniques described from FIG. 1-FIG. 9. For example,computer system 10 may be used to implement the functionality of LiDARcontroller 206 and to perform the operations of method 900.

The subsystems shown in FIG. 10 are interconnected via a system bus 75.Additional subsystems such as a printer 74, keyboard 78, storagedevice(s) 79, monitor 76, which is coupled to display adapter 82, andothers are shown. Peripherals and input/output (I/O) devices, whichcouple to I/O controller 71, may be connected to the computer system byany number of means known in the art such as input/output (I/O) port 77(e.g., USB, FireWire®). For example, I/O port 77 or external interface81 (e.g. Ethernet, Wi-Fi, etc.) may be used to connect computer system10 to a wide area network such as the Internet, a mouse input device, ora scanner. The interconnection via system bus 75 allows the centralprocessor 73 to communicate with each subsystem and to control theexecution of a plurality of instructions from system memory 72 or thestorage device(s) 79 (e.g., a fixed disk, such as a hard drive, oroptical disk), as well as the exchange of information betweensubsystems. The system memory 72 and/or the storage device(s) 79 mayembody a computer readable medium. Another subsystem is a datacollection device 85, such as a camera, microphone, accelerometer, andthe like. Any of the data mentioned herein may be output from onecomponent to another component and may be output to the user.

A computer system may include a plurality of the same components orsubsystems, e.g., connected together by external interface 81 or by aninternal interface. In some embodiments, computer systems, subsystem, orapparatuses may communicate over a network. In such instances, onecomputer may be considered a client and another computer a server, whereeach may be part of a same computer system. A client and a server mayeach include multiple systems, subsystems, or components.

Aspects of embodiments may be implemented in the form of control logicusing hardware (e.g. an application specific integrated circuit or fieldprogrammable gate array) and/or using computer software with a generallyprogrammable processor in a modular or integrated manner. As usedherein, a processor includes a single-core processor, multi-coreprocessor on a same integrated chip, or multiple processing units on asingle circuit board or networked. Based on the disclosure and teachingsprovided herein, a person of ordinary skill in the art will know andappreciate other ways and/or methods to implement embodiments of thepresent invention using hardware and a combination of hardware andsoftware.

Any of the software components or functions described in thisapplication may be implemented as software code to be executed by aprocessor using any suitable computer language such as, for example,Java, C, C++, C#, Objective-C, Swift, or scripting language such as Perlor Python using, for example, conventional or object-orientedtechniques. The software code may be stored as a series of instructionsor commands on a computer readable medium for storage and/ortransmission. A suitable non-transitory computer readable medium mayinclude random access memory (RAM), a read only memory (ROM), a magneticmedium such as a hard-drive or a floppy disk, or an optical medium suchas a compact disk (CD) or DVD (digital versatile disk), flash memory,and the like. The computer readable medium may be any combination ofsuch storage or transmission devices.

Such programs may also be encoded and transmitted using carrier signalsadapted for transmission via wired, optical, and/or wireless networksconforming to a variety of protocols, including the Internet. As such, acomputer readable medium may be created using a data signal encoded withsuch programs. Computer readable media encoded with the program code maybe packaged with a compatible device or provided separately from otherdevices (e.g., via Internet download). Any such computer readable mediummay reside on or within a single computer product (e.g. a hard drive, aCD, or an entire computer system), and may be present on or withindifferent computer products within a system or network. A computersystem may include a monitor, printer, or other suitable display forproviding any of the results mentioned herein to a user.

In some embodiments, LiDAR system 102 may have a semi-coaxial LiDARstructure where the system uses a MEMS system for one-dimensionscanning, as part of the transmitting system, and a mechanical systemfor another dimension scanning (e.g., a dimension orthogonal to thefirst dimension scanning) that shares a motor with a receiving apertureof the receiving system. For example, light may be first steered by aMEMS scanner in x-axis direction, and then be scanned by a galvo systemin y-axis direction orthogonal to x-axis direction, in a cascadedfashion. Light reflected by an object may be de-scanned in y-axisdirection by the receiving aperture rotated by the same galvo system.The reflected light may then be collected by detectors (e.g., a detectorarray).

By combining only one-dimension scanning of the transmitting system withthe receiving system, the mechanical part of the transmitting system canscan at a relatively low rate (e.g., 10 Hz) and thus reduce the powerconsumption and increase the lifetime and reliability of the system.Also, the size of the mirror aperture of the mechanical part can belarger than the mirror aperture of the MEMS system because of therelatively low scanning rate. Moreover, for future improving the LiDARsystem's performance purpose, the size of the mirror aperture of themechanical system can also further be extended. In some embodiments,silicon (Si) may be used for building structures that drive the mirrorfor the high frequency axial scanning. For example, Si may be used forbuilding structures that drive the MEMS system. Because Si madestructures have a much higher fatigue resistance comparing to metal madestructures, using Si for building structures that drive the highfrequency axial scanning may significantly extend the lifetime of thescanning structure. Also, using Si may increase the system's magnetismresistance, temperature stability, overall reliability and reduce theweight, and the power consumption, it is suitable for the fast axisscanning. However, due to the manufacturing restrictions, the scale ofthe MEMS system can not be larger than a few centimeters (e.g., around 5centimeters), using a mechanical system to combine with the MEMS systemfor both transmitting and receiving (e.g., the semi-coaxial structurescanning system) may greatly increase the size of the transmitting andreceiving apertures and the mechanical stability of the system. Largerreceiving apertures may increase the signal-to-noise ratio (SNR),detection distance, probability of detection (e.g., more than 80% forthe systems disclosed in details in FIGS. 11 and 12), reduce the falseacceptance rate (e.g., reduce the possibility of false detection ofnon-existence object) and increase the precision of the measuringsystem. Also, the detection SNR, probability of detection, and detectiondistance can be further increased by increasing the aperture of themechanical scanner's size, which makes the system specificationexpandable. As a result, by semi-coaxial the MEMS system and themechanical system (e.g., using the MEMS system with high a fatigueresistance but smaller aperture size to scan the high frequency scanningdiminution, and using the mechanical system with larger apertures sizeto scan and descan the low frequency scanning diminution), thesemi-coaxial system may benefit from both systems' advantages whileovercoming the shortcomings of each individual system.

FIG. 11 illustrates examples of internal components of an embodiment ofLiDAR system 102. LiDAR system 102 includes a transmitting system 1102(a transmitter), a receiving system 1104 (a detector), controllers (notshown) which control the operations of transmitting system 1102 andreceiving system 1104 respectively. Transmitting system 1102 includes alight source 1128, a first mirror rotated by a MEMS system 1132, asecond mirror 1135 and in some embodiments, a collimator lens (notshown). In some embodiments, light source 1128 may be at least one ofpulsed laser diode, source of FMCW signal, or AMCW signal, etc.Receiving system 1104 includes a receiving aperture 1134, collimatorlens 1130 and a photodetector 1136. LiDAR system 102 further includes, asubstrate 1138 rotated by a motor 1133 where second mirror 1135 andreceiving aperture 1134 are placed on substrate 1138 at a firstdistance. The first mirror and second mirror 1135 are placed in a seconddistance where the first distance and the second distance are set in amanner that receiving aperture 1134 may receive the light beam emittedby light source 1128, reflected by the first mirror of MEMS system 1132and objects to be scanned. In some embodiments, LiDAR system 102,transmitting system 1102 and receiving system 1104 can be configured asa semi-coaxial system to share only one dimension of scanning anddescanning (e.g., in x direction as shown in FIG. 11) to perform lightsteering operation. In some embodiments, second mirror 1135 andreceiving aperture 1134 may be a combined aperture. For example,substrate 1138 may include only one aperture 1134 that is used for bothreflecting the light beam emitted by light source 1128 and receiving thelight beam reflected by the object to be scanned.

MEMS system 1132 may include one or more rotatable mirrors. FIG. 11illustrates MEMS system 1132 as having one mirror. In some embodiments,MEMS system 1132 may include a plurality of mirrors. In one example, themirror aperture of MEMS system 1132 may be a 1 mm×10 mm pulsed laserdiode with a +/−3.75° mechanical tilt. In some embodiments, MEMS system1132 may be rotated at a frequency close to the natural frequency of therotatable mirror. For example, for forming a 45° horizontal FOV, theresonant frequency may be set as 5 kHz. For forming a 60° horizontalFOV, the resonant frequency may be set as 6.7 kHz. For forming a 75°horizontal FOV, the resonant frequency may be set as 8 kHz. In someembodiments, the required torque for rotating the mirror may be lessthan 0.5 u Nm.

In some embodiments, MEMS system 1132 and motor 1133 further bothinclude an actuator (not shown in FIG. 11) to rotate the rotatablemirrors. In some embodiments, the actuators are controlled bycontrollers that the light beam transmitted from the transmitting systemmay form a FOV 1152. In some embodiments, MEMS system 1132 can rotatethe first rotatable mirror around a first axis 1142 to change a firstangle of output light beams 1118 with respect to a first dimension(e.g., the y-axis). Motor 1133 can rotate second mirror 1135 andreceiving aperture 1134 around a second axis 1146 to set a second anglewith respect to a second dimension (e.g., the x-axis). The controllerscan control the actuators to produce different combinations of angles ofrotation around first axis 1142 and second axis 1146 such that themovement of output light beams 1118 can follow scanning patterncorresponding to FOV 1152. A range 1154 of movement of output light beam1118 along the x-axis, as well as a range 1158 of movement of outputlight beams 1118 along the y-axis, can define a FOV. An object withinthe FOV, can receive and reflect output light beams 1118 to form areflected light signal, which can be received by receiving system 1104.

In some embodiments, light source 1128 may include more than one lightsources, such that transmitting system 1102 may form a split FOV. Forexample, as shown in FIG. 11, light source 1128 may include two pulsedlaser diodes (PLDs) that can generate output light 1118 that includestwo respective light beams. By adjusting the two respective light beamsusing transmitting system 1102, a split FOV 1158A and 1158B may beformed. For example, output light 1118 from one of the two PLD may besteered by MEMS system 1132 onto the angle from −23 degrees to −10.5degrees, and output light 1118 from the other PLD may be steered ontothe angle from −10.5 degrees to 3.5 degrees. The full covering range maybe 26.5 degrees in y-axis. Thus, as a result, MEMS system 1132 may needto rotate in a smaller range to form the same range of FOV as if splitFOV is not used. This may further reduce the power consumption, thetorque needed for rotating the mirror and thus increase the lifetime ofthe MEMS system.

In some embodiments, two detectors (e.g., photodetector 1136 may includetwo detector arrays) may be used to receive the two output light beamsemitted by the two light sources respectively. In some embodiments, thenumber of detector arrays in detectors (e.g., photodetector 1136) may bethe same as the number of light source 1128. In some embodiments, thedetectors may be two arrays of avalanche photodiodes (APD) that arealigned with the two PLDs respectively. In some embodiments, thereceiver of each detector within the detector array may has a smallangle of view (e.g., less than few centimeters) such that the signal tonoise ratio of receiving system 1104 may be increased.

In some embodiments, LiDAR system 102 may has a spinning structure wherethe system uses a MEMS system for one-dimension scanning, as part of thetransmitting system, and where the MEMS system is rotated along with thereceiving system by a motor in another dimension orthogonal to the firstdimension. For example, light may be first steered by a MEMS scanner inx-axis direction, and then be scanned by a galvo system in y-axisdirection orthogonal to x-axis direction, in a cascaded fashion. Lightreflected by an object may be descanned in y-axis direction with areceiving aperture. The reflected light may then be collected by one ormore detectors (e.g., detector array).

FIG. 12 illustrates examples of internal components of an embodiment ofLiDAR system 102. LiDAR system 102 includes a transmitting system 1202(a transmitter), a receiving system 1204 (a detector), a controller (notshown) which controls the operations of transmitting system 1202 andreceiving system 1204 respectively. Transmitting system 1202 includes alight source 1238, a mirror rotated by a MEMS system 1242 and in someembodiments, a collimator lens (not shown). In some embodiments, lightsource 1238 may be at least one of pulsed laser diode, source of FMCWsignal, or AMCW signal, etc. Receiving system 1204 includes a receivingaperture (not shown), collimator lens (not shown) and a photodetector(not shown). LiDAR system 102 further includes, a substrate 1248 rotatedby a motor 1243 where MEMS system 1242 and receiving system 1204 areplaced on substrate 1248 at a first distance. Light source 1238 andsubstrate 1248 are placed in a second distance where the first distanceand the second distance are set in a manner that receiving system 1204may receive the light beam emitted by light source 1238 and reflected byMEMS system 1242 and objects to be scanned. In some embodiments,transmitting system 1202 and receiving system 1204 can be configured asone spinning system where MEMS system 1242 scans in one dimension whilespinning along with receiving system 1204 in another dimension at thesame time.

MEMS system 1242 may include one or more rotatable mirrors. FIG. 12illustrates MEMS system 1242 as having one mirror. In some embodiments,MEMS system 1242 may include a plurality of mirrors. In one example, themirror aperture of MEMS system 1242 may be a 1 mm×10 mm pulsed laserdiode with a +/−3.75° mechanical tilt. In some embodiments, MEMS system1242 may be rotated at a frequency close to the natural frequency of therotatable mirror. For example, for forming a 45° horizontal FOV, theresonant frequency may be set as 5 kHz. For forming a 60° horizontalFOV, the resonant frequency may be set as 6.7 kHz. For forming a 75°horizontal FOV, the resonant frequency may be set as 8 kHz. In someembodiments, the required torque for rotating the mirror may be lessthan 0.5 u Nm.

In some embodiments, MEMS system 1242 and motor 1243 further bothinclude an actuator (not shown) to rotate the rotatable mirror andsubstrate 1248, respectively. In some embodiments, the actuators arecontrolled by one or more controllers that the light beam transmittedfrom the transmitting system may form a FOV 1262. In some embodiments,MEMS system 1242 can rotate the rotatable mirror around a first axis1252 to change a first angle of output light beams 1218 with respect toa first dimension (e.g., the y-axis). Motor 1243 can rotate MEMS system1242 and receiving system 1204 around a second axis 1256 with respect toa second angle in a second dimension (e.g., the x-axis). The controllerscan control the actuators to produce different combinations of angles ofrotation around first axis 1252 and second axis 1256 such that themovement of output light beams 1218 can follow scanning patterncorresponding to FOV 1262. A range 1264 of movement of output lightbeams 1218 along the x-axis, as well as a range 1268 of movement ofoutput light beams 1218 along the y-axis, can define a FOV. An objectwithin the FOV, can receive and reflect output light beams 1218 to forma reflected light signal, which can be received by receiving system1204.

In some embodiments, light source 1238 may include more than one lightsources to form a split FOV. For example, as shown in FIG. 12, lightsource 1238 may include two PLDs that can generate output light beams1218 that include two respective light beams. By adjusting the tworespective light beams using transmitting system 1202, a split FOV 1268Aand 1268B may be formed. For example, output light 1218 from one of thetwo PLD may be steered by MEMS system 1232 onto the angle from −23degrees to −10.5 degrees, and output light 1218 from the other PLD maybe steered onto the angle from −10.5 degrees to 3.5 degrees. The fullcovering range may be 26.5 degrees in y-axis. Thus, as a result, MEMSsystem 1232 may need to rotate in a smaller range to form the same rangeof FOV as if split FOV is not used.

In some embodiments, two detectors (as shown in FIG. 12) may be used toreceive the two output light beams emitted by the two light sourcesrespectively. In some embodiments, the detectors may be two arrays ofAPD that are aligned with the two PLD respectively.

FIG. 13 illustrates a flowchart of method of operating a mirrorassembly, according to embodiments of the disclosure. FIG. 13 shows asimplified flow diagram of method 1300 for performing light steeringoperation using a LiDAR system 102, such as LiDAR systems shown in FIG.11 and FIG. 12.

At operation 1302, a controller determines a first angle and a secondangle of a light path. In some embodiments, the light path may be one ofa projection paths for output light or an input path of input light, thefirst angle may be with respect to a first dimension and the secondangle may be with respect to a second dimension orthogonal to the firstdimension. The first angle may be set according to a scanning pattern(e.g., a sinusoidal scanning trajectory along the fast axis). The secondangle may be set according to the scanning pattern (e.g., sawtoothscanning trajectory or a triangle scanning trajectory along the slowaxis).

At operation 1304, the controller controls a first actuator to rotate afirst rotatable mirror of the MEMS to set the first angle. Thecontroller may also control the first actuator to exert a torque to thefirst rotatable mirror as a quasi-static load.

At operation 1306, the controller controls a non-MEMS system to set thesecond angle. In some embodiments, the controller may control the secondactuator to exert a torque to a second rotatable mirror using a non-MEMSsystem (e.g., a galvanometer mirror or a polygon mirror). In some otherembodiments, the controller may change the mirror within a flash system(e.g., an array of identical mirrors) to move the light beam within thescanning pattern. In some embodiments, the controller may control thesecond actuator to exert a torque to the second rotatable mirror using aMEMS, similar to control the first rotatable mirror of the MEMS to setthe first angle. In some embodiments, the controller may control a motorwhere the MEMS system is mounted to set the second angle.

At operation 1308, the controller uses the first rotatable mirror set atthe first angle and the second actuator to set at the second angle toperform at least one of: reflecting the output light from the lightsource along the projection path towards an object or reflecting theinput light propagating along the input path to a receiver. For example,the controller may control a light source to project a light beamincluding a light signal towards the mirror assembly. The light sourcemay include a pulsed laser diode, a source of FMCW signal, a source ofAMCW signal, etc.

At operation 1310, the controller controls a detector of the non-MEMSsystem to receive a reflection of the light beam, reflected by a distantobject. For example, an object within a FOV may be detected byreflecting the light beam back to the detector.

Any of the methods described herein may be totally or partiallyperformed with a computer system including one or more processors, whichmay be configured to perform the steps. Thus, embodiments may bedirected to computer systems configured to perform the steps of any ofthe methods described herein, potentially with different componentsperforming a respective step or a respective group of steps. Althoughpresented as numbered steps, steps of methods herein may be performed ata same time or in a different order. Additionally, portions of thesesteps may be used with portions of other steps from other methods. Also,all or portions of a step may be optional. Additionally, any of thesteps of any of the methods may be performed with modules, units,circuits, or other means for performing these steps.

Other variations are within the spirit of the present disclosure. Thus,while the disclosed techniques are susceptible to various modificationsand alternative constructions, certain illustrated embodiments thereofare shown in the drawings and have been described above in detail. Itshould be understood, however, that there is no intention to limit thedisclosure to the specific form or forms disclosed, but on the contrary,the intention is to cover all modifications, alternative constructionsand equivalents falling within the spirit and scope of the disclosure,as defined in the appended claims. For instance, any of the embodiments,alternative embodiments, etc., and the concepts thereof may be appliedto any other embodiments described and/or within the spirit and scope ofthe disclosure.

The use of the terms “a” and “an” and “the” and similar referents in thecontext of describing the disclosed embodiments (especially in thecontext of the following claims) are to be construed to cover both thesingular and the plural, unless otherwise indicated herein or clearlycontradicted by context. The terms “comprising,” “having,” “including,”and “containing” are to be construed as open-ended terms (i.e., meaning“including, but not limited to,”) unless otherwise noted. The term“connected” is to be construed as partly or wholly contained within,attached to, or joined together, even if there is something intervening.The phrase “based on” should be understood to be open-ended, and notlimiting in any way, and is intended to be interpreted or otherwise readas “based at least in part on,” where appropriate. Recitation of rangesof values herein are merely intended to serve as a shorthand method ofreferring individually to each separate value falling within the range,unless otherwise indicated herein, and each separate value isincorporated into the specification as if it were individually recitedherein. All methods described herein may be performed in any suitableorder unless otherwise indicated herein or otherwise clearlycontradicted by context. The use of any and all examples, or exemplarylanguage (e.g., “such as”) provided herein, is intended merely to betterilluminate embodiments of the disclosure and does not pose a limitationon the scope of the disclosure unless otherwise claimed. No language inthe specification should be construed as indicating any non-claimedelement as essential to the practice of the disclosure.

What is claimed is:
 1. A Light Detection and Ranging (LiDAR) systemcomprising: a light source configured to emit a light beam; a firstapparatus configured to adjust the light beam, comprising: a firstrotatable mirror configured to receive and reflect the light beam; and afirst actuator configured to rotate the first rotatable mirror; and asecond apparatus configured to adjust the light beam and receive thelight beam from the first rotatable mirror and reflected by an object,comprising: a second rotatable mirror configured to receive andpropagate the light beam; a receiving mirror configured to receive andreflect the light beam reflected by the object; and a second actuatorconfigured to adjust the second rotatable mirror and the receivingmirror; and a detector configured to receive the light beam reflected bythe object from the receiving mirror.
 2. The LiDAR system of claim 1,wherein the first rotatable mirror and the second rotatable mirror areconfigured to set a first angle of light path of the light beam withrespect to a first dimension and to set a second angle of the light pathof the light beam with respect to a second dimension orthogonal to thefirst dimension respectively.
 3. The LiDAR system of claim 2, whereinthe first and second apparatus further comprise at least one controllerrespectively, and wherein the at least one controller is configured to:control the first actuator and the second actuator to output a firstlight including a first light signal at a first time point along thelight path towards an object; control the first actuator and the secondactuator to select a second light including a second light signalpropagating along the light path from the object; receive, via thedetector, the second light at a second time point; and determine alocation of the object with respect to the LiDAR module based on adifference between the first time point and the second time point, thefirst angle, and the second angle.
 4. The LiDAR system of claim 3,wherein the first apparatus comprises a MEMS system, and wherein thesecond apparatus comprising at least one of a galvanometer mirror, amirror polygon, or a wavelength scanning element.
 5. The LiDAR system ofclaim 1, wherein the further comprising a substrate, wherein the secondrotatable mirror and the receiving mirror are placed on the substrate,wherein the second rotatable mirror is separated from the receivingmirror by a first distance, wherein the first rotatable mirror and thesubstrate are separated by a second distance, and wherein the firstdistance and the second distance are set based on an angle of incidenceof the light beam from the light source with respect to the firstrotatable mirror.
 6. The LiDAR system of claim 5, wherein the detectorcomprises a plurality of avalanche photodiodes and wherein the secondrotatable mirror and the receiving mirror share at least an aperture. 7.The LiDAR system of claim 6, wherein the light source comprises at leastone of a plurality of laser diodes, fiber lasers or vertical-cavitysurface-emitting lasers, wherein the detector comprises a plurality ofarray of detectors, and wherein the number of the light sources equalsto the number of arrays of detectors.
 8. The LiDAR system of claim 1,wherein the second actuator comprises at least one of a comb drive, apiezoelectric device, or an electromagnetic device.
 9. The LiDAR systemof claim 7, wherein a mass of the first rotatable mirror is smaller thana mass of the second rotatable mirror; wherein the at least onecontroller is configured to adjust a first rotation angle of the firstrotatable mirror at a first frequency, the first frequency beingsubstantially equal to a natural frequency of the first rotatablemirror; and wherein the at least one controller is configured to adjusta second rotation angle of the second rotatable mirror at a secondfrequency lower than the first frequency.
 10. The LiDAR system of claim7, wherein the first actuator and the second actuator comprise a rotarydrive; and wherein the at least one controller is configured to adjustthe first rotation angle and the second rotation angle based onadjusting, respectively, a first torque provided by the first actuatorand a second torque provided by the second actuator.
 11. The LiDARsystem of claim 1, further comprising motion sensors, each motion sensorbeing coupled with each of the first rotatable mirror and the secondrotatable mirror and configured to measure a rotation angle of the firstrotatable mirror and the second rotatable mirror.
 12. A Light Detectionand Ranging (LiDAR) system comprising: a light source configured to emita light beam; and a light adjusting apparatus comprising: a motorconfigured to rotate the aperture in the first direction; amicroelectromechanical system (MEMS) comprising: a rotatable mirrorrotatable in a second direction, orthogonal to the first direction,configured to receive and reflect a light beam projected by the lightsource; and an actuator configured to rotate the rotatable mirror in thesecond direction; and a detector configured to receive a light beamreflected by an object.
 13. The LiDAR system of claim 12 furthercomprising at least one controller, and wherein the controller isconfigured to: control the motor and the actuator to output a firstlight including a first light signal at a first time point along thelight path towards the object; receive, via the detector, the secondlight at a second time point; and determine a location of the objectwith respect to the LiDAR system based on a difference between the firsttime point and the second time point, the first angle, and the secondangle.
 14. The LiDAR system of claim 13, wherein the detector comprisesa plurality of avalanche photodiodes.
 15. The LiDAR system of claim 14,wherein the light source comprises at least one of a plurality of laserdiodes, fiber lasers or vertical-cavity surface-emitting lasers.
 16. TheLiDAR system of claim 15, wherein the at least one controller isconfigured to adjust a first rotation angle of the rotatable mirror at afirst frequency, the first frequency being substantially equal to anatural frequency of the rotatable mirror; and wherein the at least onecontroller is configured to adjust a second rotation angle of the motorat a second frequency lower than the first frequency.
 17. The LiDARsystem of claim 16, wherein the actuator and the motor comprise a rotarydrive; and wherein the at least one controller is configured to adjustthe first rotation angle and the second rotation angle based onadjusting, respectively, a first torque provided by the actuator and asecond torque provided by the motor.
 18. The LiDAR system of claim 17,wherein the motor comprises at least one of a comb drive, apiezoelectric device, or an electromagnetic device.
 19. A method foradjusting a light beam in a semi-coaxial architecture light steeringsystem, comprising: determining a first angle and a second angle of alight path, the light path being a projection path for an output lightor an input path of an input light, the first angle being with respectto a first dimension, the second angle being with respect to a seconddimension orthogonal to the first dimension; controlling a firstactuator to rotate a first rotatable micro-mirror of amicroelectromechanical system (MEMS) to set the first angle; controllinga non-MEMS system to set the second angle; projecting, using a lightsource, a light beam including at least one light signal towards amirror assembly, corresponding to the controlled first actuator and thecontrolled non-MEMS system at the set first and second angle; andreceiving a reflection of the light beam, reflected by an object, by adetector comprised by the non-MEMS system.
 20. The method of claim 19,further comprising: adjusting a first rotation angle of the firstrotatable mirror at a first frequency; and adjusting a second rotationangle of the second rotatable mirror at a second frequency lower thanthe first frequency, the first frequency being substantially equal to anatural frequency of the first rotatable micro-mirror.